This invention relates to power converters, and more particularly to a circuit for efficient use of transistor switches to chop DC power from a source, and a voltage multiplying diode rectifying ladder network to rectify and filter the chopped power delivered to a load.
Photo flash units for camera, geiger counters, and other electronic equipment require a source of high voltage DC current to operate. Since the primary source is often an inexpensive low voltage battery, a step-up DC-to-DC converter is required. Long battery life is usually desirable and therefore a high conversion efficiency is required. This invention meets these requirements.
About one-half of the present integrated circuit equipments require, in addition to a low voltage source (such as +5 VDC), a higher voltage source (such as +10 VDC, -10 VDC, or -15 VDC). This is also true of many of the microprocessors which are currently in popular demand. To supply these higher voltage and mixed power requirements, power supplies using AC inputs with transformer-rectifiers, multi-battery packs, or DC-to-DC converters are available; however, they have undesirable features, such as: requiring a source of AC voltage; transformers that are large or heavy; designs that are costly; and/or do not have a high conversion efficiency. There is a need for a step-up DC-to-AC or DC-to-DC converter that is not only efficient and inexpensive, but also light and not bulky, i.e., implemented without a transformer.
One application of particularly high potential use is in the displays for electronic calculators and instrument displays. There are four types of displays currently available: LED (light emitting diode); LCD (liquid crystal display); fluorescent; and neon. To date, the market prefers LEDs and LCDs, although some products, like pocket calculators and cash registers, are using fluorescent displays which are aesthetically pleasing and brighter than LEDs. LEDs operate on low voltage, but have a high current drain upon the battery and present a rather harsh display. LCDs still have cost, response time, and temperature characteristic problems. And while neon displays have none of these drawbacks, they need a very efficient DC-to-DC step-up converter to operate from a low cost, low voltage battery source because they require 180 VDC starting potential. This invention may supply this need for neon displays. Many fluorescent lighting fixtures also require a source of high voltage for starting current. Cathode ray tubes, television picture tubes, and photo multipliers also require a high voltage, low current source. The list of potential users of this invention is extensive. For example, the invention was first developed and used to supply a 12 volt negative DC source to circuitry in a television test signal generator. The invention was next used as a DC-to-AC inverter to power a gyro used on a remotely piloted airplane. Other immediate uses are contemplated wherever conversion of DC power is required, especially for battery operated systems which are weight and size limited and require high conversion efficiency to conserve battery power. Prior state-of-the-art systems tend to be heavier and less efficient than desired for spacecraft and other lightweight applications. Use is also contemplated whenever an efficient DC-to-AC conversion is required such as the gyro application mentioned above, in which case the circuit is often called an inverter.